Most modern aircraft have landing gear that includes measurement means for measuring values of parameters that are monitored in order to ensure that the landing gear is used under conditions that enable predetermined safety, maintenance, and operating cost targets to be reached. By way of example, the parameters that are measured may be brake temperature, carbon disk wear when the brakes are carbon disk brakes, the pressure and the temperature of shock absorbers in the landing gear, the pressure of the gas inflating the tires of wheels, etc.
The gas pressure in the tires of wheels of an aircraft constitutes a parameter that is particularly critical, and it needs to be monitored regularly. On takeoff, a tire that is under-inflated, or indeed over-inflated, presents a major risk of bursting and projecting debris that might damage various pieces of equipment of the aircraft. In addition, regular use of tires that are under-inflated or over-inflated leads to premature wear of the tires, and thus to large extra operating costs.
It is nowadays mandatory to measure the pressure of each tire of an aircraft's wheels before each flight. For this purpose, it is either possible to provide the aircraft with onboard means enabling pressure to be measured continuously and enabling pressure measurements to be transmitted to the cockpit, or else to take measurements manually during maintenance operations while the airplane is on the ground. In both situations, use is made of a duct provided in the rim of each wheel, similar to that used for inflating the tire, which duct serves to put the inside of the tire into communication with a pressure sensor.
The measured pressure value is naturally highly dependent on the temperature of the gas, which itself depends on outside temperature, and which may be influenced to a large extent by energy from a braking operation prior to taking the measurement, etc.
It is thus essential either to correct the pressure measurement as a function of temperature, or to define thresholds that depend on temperature beyond which the tire needs to be reinflated or deflated. For this purpose, it is necessary to measure or to evaluate the temperature of the tire when measuring its pressure, thereby making onboard means more complex or lengthening the time taken for maintenance operations. An estimate of the inflation pressure of a tire can thus be obtained very simply on the basis of the position of an indicator member.